Loud speaker



E'WA L D 9 7. Y 1 R ME 3 0 0 N 00 TF R w uw ml G n w 0 m Filed Nov. 6,1924 Sept. 11, 1928.

Patented Sept. 11, 1928.

UNITED STATES PATENT OFFICE.

WOLFGANG FELIN EWALD, OF BERLIN, GERMANY, ASSIGNOR 'I'O GESELLSCHAF'IFUR DRAHTLOSE TELEGRAPHIE M. B. H., OF BERLIN, GERMANY, A CORPORATION OIGERMANY.

' LOUD SPEAKER.

Application filed November 6, 1924, Serial No 748,007, and in GermanyNovember 8, 1923.

The present patent application relates to a loudspeaking telephone whichdlfl'ers from the known arrangements in that, instead of the horncausing a distortion of tone and also 6 disturbing extraneous noises, anarrangement is employed by which a. natural reproduction of sound'andgood amplification is possible.

According to the invention the source of 10 sound is' arranged at thefocus of a conoid or paraboloid produced by the rotation of a parabolaround its axis, in such a. way that the source of sound is mechanicallycountercoupled to the reflector of sound by means of a damping kind ofsuspension. In

this way it is possible to attain a total reflection of the sound waveswithout influenc ing the character of sound, furthermore the usual hornswhich, up till now, have caused 21 disturbing noises on account of theirshape and the mechanical coupling with the source of sound areeliminated.

The annexed drawing shows an embodiment of the invention. A is'a hollowbody 25 in the shape of a paraboloid of revolution on which the soundwaves, starting from the focus F and issuing from the telephone T oranother source of sound, fall. Band C are the holding arrangements forthe source of sound T which is fastened to the reflector of sound A bymeans of damping substances D which, for instance may be made of someinelastic substance such as felt.

Spherical hollow bodies of not too large an aperture are similar inshape to the paraboloids of revolution and can therefore replace them.

Having described several embodiments of my invention, I am entitled toall other modifications as fall fairly within the scope of the followingclaims. 1. A loud speaking telephone receiver comprising a reflectorstructure having an interior surface in the form of a paraboloid, asound producing device positioned substantially at a focus thereof, andinterconnect ng supporting means therebetween comprising an inelasticmaterial.

A loud speaking telephone receiver comprising a reflecting surfacehaving a focus, a sound producing means positioned at said focus, and amechanical coupling means therebetween adapted to absorb mechanicalsound vibrations therefrom.

3. In combination a reflecting surface having a focal point. a.supporting stand therefor, a sound producing means positioned at saidfocus, and a supporting means therefor,

comprising a felt cushion.

4. loud speaking telephone reproducer comprising a curved soundreflecting surface having a focus, a sound producer including adiaphragm, positioned substantially at said focus and adapted to radiatesound vibrations toward said reflecting surface, and supporting meanstherefor, comprising supporting arms and vibration absorbent members incombination.

5. A loud speaking telephone receiver comprising a curved soundconveyingmeans, a sound producing means cooperating therewith and a mechanicalcoupling means therebetween adapted to absorb sound vibrations impressedupon the material thereof.

6. A loud speaking telephone receiver'comprising a reflecting-surfacehaving a focus. a diaphragm positioned at the focus, and

means for sup orting the diaphragm con sisting of an a sorbent materialfastened to the reflecting surface and a plurality ofradial armsconnecting the diaphragm to the absorbent material.

Da. W. F. EWALD.

